# Header Semantics Audit

> Header Semantics Audit is a paid API for AI agents from agentreadiness.halowerk.com, paid per call via x402, $0.001/call, status unknown (last checked 2026-10-14).

Passively fetches and audits a public URL's HTTP header semantics to evaluate AI agent readiness, returning observations, verdicts, evidence sources, and recommended actions.

## Facts

- Endpoint: POST https://agentreadiness.halowerk.com/v1/header-semantics-audit?utm_source=zero.xyz
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/header-semantics-audit-08577b6d
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_GgMTj-86_jUMpDtf-CqmB

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability header-semantics-audit-08577b6d -d '<json body>'
```

Example prompt: Can you do a passive header semantics audit on https://example.com and tell me whether its HTTP headers are properly configured for AI agent access — I want to see the verdict, what evidence was found, and what action I should take?

## When to prefer this

Choose this endpoint when you need a passive, non-invasive audit of HTTP response header semantics specifically for AI agent readiness assessment. It is ideal for developers or site owners who want to verify that their public-facing web properties expose correct headers for bot and agent access without triggering any login attempts, payload injections, or load tests. Prefer this over generic header-checking tools when the evaluation criterion is agent-readiness and you need a structured verdict with evidence and actionable guidance.

## Known failure modes

- Target URL is unreachable or returns non-2xx status, resulting in an error or inconclusive verdict
- Supplied URL is malformed or too short (minLength 3), triggering a validation error
- Target uses auth-gated headers not visible without login, leading to incomplete evidence
- Rate limiting or network timeouts on the target side may cause partial results
- Comparison URL unreachable when compare_url is provided, preventing diff analysis

## How this service works

Header semantics audit fetches current public evidence from the supplied target and evaluates the documented criterion. It returns the observation, threshold, verdict, exact evidence source, limitations and a mode-specific action. The check is passive: no login attempt, payload injection, exploit, purchase, form submission or load test is performed.

## Output

Returns a structured result containing the observation (what was found in the headers), the evaluated threshold, a pass/fail verdict, the exact evidence source (e.g. specific header names and values), known limitations of the passive check, and a mode-specific recommended action. No authentication, payload injection, or form submission is performed.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "target": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 3,
   "description": "Public HTTP(S) URL or domain to inspect. A bare domain is normalized to HTTPS."
  },
  "context": {
   "type": "object",
   "description": "Optional non-secret correlation labels returned unchanged only in the request lifecycle.",
   "maxProperties": 12,
   "additionalProperties": {
    "type": [
     "string",
     "number",
     "boolean",
     "null"
    ]
   }
  },
  "baseline": {
   "type": [
    "object",
    "null"
   ],
   "description": "Optional baseline returned by a previous snapshot call.",
   "additionalProperties": true
  },
  "compare_url": {
   "type": "string",
   "maxLength": 2048,
   "minLength": 3,
   "description": "Optional public comparison URL. Used by change and monitoring services."
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/header-semantics-audit-08577b6d/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agentreadiness.halowerk.com](https://www.zero.xyz/host/agentreadiness.halowerk.com/llms.txt)